1. Field of the Invention
The present invention relates to image equipment having image forming elements such as an image sensor element or a display element, and also to a vibrating device designed to vibrate the dust-screening member that is arranged at the front of each image forming element of such an image equipment.
2. Description of the Related Art
As image equipment having image forming elements, there is known an image acquisition apparatus that has an image sensor element configured to produce a video signal corresponding to the light applied to its photoelectric conversion surface. Also known is an image projector that has a display element, such as liquid crystal element, which displays an image on a screen. In recent years, image equipment having such image forming elements have been remarkably improved in terms of image quality. If dust adheres to the surface of the image forming element such as the image sensor element or display element or to the surface of the transparent member (optical element) that is positioned in front of the image forming element, the image produced will have shadows of the dust particles. This makes a great problem.
For example, digital cameras of called “lens-exchangeable type” have been put to practical use, each comprising a camera body and a photographic optical system removably attached to the camera body. The lens-exchangeable digital camera is so designed that the user can use various kinds of photographic optical systems, by removing the photographic optical system from the camera body and then attaching any other desirable photographic optical system to the camera body. When the photographic optical system is removed from the camera body, the dust floating in the environment of the camera flows into the camera body, possibly adhering to the surface of the image sensor element or to the surface of the transparent member (optical element), such as a lens, cover glass or the like, that is positioned in front of the image sensor element. The camera body contains various mechanisms, such as a shutter and a diaphragm mechanism. As these mechanisms operate, they produce dust, which may adhere to the surface of the image sensor element as well.
Projectors have been put to practical use, too, each configured to enlarge an image displayed by a display element (e.g., CRT or liquid crystal element) and project the image onto a screen so that the enlarged image may be viewed. In such a projector, too, dust may adhere to the surface of the display element or to the surface of the transparent member (optical element), such as a lens, cover glass or the like, that is positioned in front of the display element, and enlarged shadows of the dust particles may inevitably be projected to the screen.
Various types of mechanisms that remove dust from the surface of the image forming element or the transparent member (optical element) that is positioned in front of the image sensor element, provided in such image equipment have been developed.
For example, US 2008/0018775 A1 discloses an image pickup unit 400 including an optical lowpass filter 410, a piezoelectric element 430, and an image pickup element 33, and the like as units. The optical lowpass filter 410 is separated into a plurality of optical members in the photographic optical axis direction. That is, the optical lowpass filter 410 includes a first grouped optical member 411, a second grouped optical member 412, and a third grouped optical member 413. The first grouped optical member 411 is given vibration in the direction perpendicular to the photographic optical axis by the piezoelectric element 430 to remove foreign substances such as dust adhering to the surface of the optical member. In the image pickup unit 400, the first grouped optical member 411 is formed from a birefringent plate made of crystal having a single crystal structure. Such a birefringent plate can be vibrated more efficiently than, for example, glass that is an amorphous material because of a higher Q value representing the sharpness of resonance and the difficulty in attenuating vibration.
In the image pickup unit 400 disclosed in US 2008/0018775 A1, a vibration transfer member 431 having an almost L-shaped section is bonded and fixed to the upper side of the first grouped optical member 411 included in the optical lowpass filter 410. A biasing force transfer member 441 having an almost L-shaped section is bonded and fixed to the lower side of the first grouped optical member 411 on the opposite side. A container portion 421 configured to store the piezoelectric element 430 is formed on the upper side of a frame portion 420a of a lowpass filter holding member 420 that holds the optical lowpass filter 410. One end face of the piezoelectric element 430 is fixed to the frame portion 420a by bonding or the like. In this case, the piezoelectric element 430 is held such that expansion occurs in a direction (the vertical direction of the camera) perpendicular to the photographic optical axis upon voltage application. In addition, the first grouped optical member 411 is arranged between an image pickup element holding member 510 and an arm portion 460c of a regulation member 460. The first grouped optical member 411 is fixed by fixing the regulation member 460 to the image pickup element holding member 510 by a screw 550.